Conventional wheel and tire assemblies used to support a motor vehicle include a tubeless tire having a bead that seals to a wheel flange in order to maintain a desirable air pressure between the tire and wheel. In mass production settings, it is necessary to inflate the tire rapidly in order to prevent a bottleneck in the assembly process. To rapidly inflate the tire, a bell, which circumscribes a wheel, is lowered to depress the tire separating the tire bead from the wheel flange. The bell forms a sealed enclosure with the tire interior enabling pressurized air to be injected through the bell into the tire interior at a high pressure and rate. The cavity formed between the bell and the tire interior is pressurized to a level slightly above the desired inflation pressure of the tire. Subsequent to pressurizing this cavity, the bell is rapidly withdrawn from the tire allowing the tire bead to seal against the wheel flange, trapping the pressurized air between the tire and the wheel at the desired pressure.
In recent years, vehicle-manufacturing processes have advanced to allow for the production of multiple vehicles on the same assembly line such as, for example, a truck and a compact car. Therefore, it has become necessary to inflate larger ranges of tire sizes on the same assembly line. One type of bell assembly capable of inflating large ranges of tire sizes utilizes a first bell and a second bell slidably disposed within the first bell. The second bell includes a smaller diameter than the first bell and is used to inflate small diameter tires. The first bell having a larger diameter than the second bell is used to inflate larger diameter tires.
When inflating larger diameter tires, the second bell is retracted within the first bell so that the first bell depresses the large diameter tire to inflate the tire as set forth above. When inflating a smaller diameter tire, the second bell is extended to a position beyond the first bell so that the second bell only is used to inflate the smaller diameter tire. Bell assemblies of this type are disclosed in U.S. Pat. Nos. 6,029,716, 6,467,524, 6,463,982, and 6,502,618.
To establish a sufficient seal with the smaller diameter tires, it is necessary to provide sufficient force to the second bell to prevent air leakage during the inflation process. The prior art patents listed above disclose various methods for establishing a depression force that are primarily fluidic in nature. Providing a depression force to the second bell in this manner result in several drawbacks that could cause an inconsistent depression force upon a tire being inflated. For example, disruption in fluid supply or degradation of a fluid seal can result in the loss of depression force provided to the second bell. This could result in inadequate pressurization of the tire. Therefore, it would be desirable to provide a consistent yet simple assembly to provide a consistent depression force to the second bell.